Fluid systems (e.g., fuel systems, propulsion systems, hydraulic systems, etc.) often employ fluid devices (e.g., check valves) to prevent reverse fluid flow through the system. For example, a space shuttle propulsion system may employ check valves to prevent reverse fluid flow to a main engine of a space shuttle. Check valves typically include a ball valve that moves relative to a valve seat to control fluid flow through the check valve. In some examples, a spring is often employed to bias the ball valve into sealing engagement with the valve seat. In some examples, the spring may be adjustable to vary a preload to adjust or set a desired cracking pressure of the valve (i.e., a pressure at which the ball valve moves to an open position away from the valve seat to allow fluid through the valve). However, in some instances, the spring may wear or fracture due to cyclic fatigue or cryogenic shock. As a result, the valve may open at a pressure less than the desired cracking pressure provided by the initial preload or, alternatively, there may be reverse flow (fluid flow from the outlet toward the inlet). In some instances, a change in pressure across an orifice of the fluid valve may produce vibration having a frequency similar or the same as a resonant frequency of the spring, which causes chattering. In some instances, for example during high vibrational applications, the ball valve may dislodge (e.g., from the impetus of the spring) and fall from the valve seat.
Some known check valves employ a spring-biased swing flapper. However, in some applications, fluid flow may cause cyclic wear on the spring and/or flapper due to spring-flapper oscillations. In some examples, springless or spring-free check valves employ a flap that moves or deflects relative to a valve seat to control fluid flow. However, a cracking pressure of springless check valves may not be adjustable. In some instances, the flaps could chatter and/or become damaged during high vibrational applications. Thus, the flap may be subject to chatter during certain flow conditions that prevent the flap from providing a desired shut-off or seal.